Chrysler, a unit of Italian company Fiat Chrysler, said it sold 166,596 units last month, its best May sales since 2007.
The increase was stronger than the 14.4 percent rise estimated by car-shopping website Edmunds.com.
The number-three US automaker said sales of Jeep sport utility vehicles jumped 58 percent, the largest increase of any Chrysler Group brands. It was Jeep's third consecutive month of record sales.
Ram pickup truck sales rose 17 percent.
"Our Jeep sport-utility vehicles and Ram pickups continued to do well in May as our dealers reported brisk May sales over five weekends and the Memorial Day holiday," said Reid Bigland, head of US sales.
Chrysler was the first to publish US sales in May on Tuesday; other automakers were due to release their data later in the day.
Edmunds.com estimates overall US vehicle sales slowed to a 7.3 percent year-over-rise in May from a gain of 8.1 percent in April.